1. Field of the Invention
The present invention relates generally to an assembly and method used to improve electric motor performance and reliability. This invention relates specifically to an assembly and method of implementing jet impingement cooling for the removal of dissipated heat from the end-windings of a sealed electric motor, operating in a harsh environment such as an automotive vehicle.
2. Background
Electric motors are used as the driving means for everything from electric vehicles to domestic appliances. Improvements in electric motor performance and reliability for all types of electric motors are desired. The presence of high power levels of electric motors results in high temperature operation which causes distortions in the operating characteristics of the motor. In the absence of heat removal liberated during motor operation, poor, degraded performance, and possibly total motor failure may result. As electronic device technology advances, there is a continuous reduction in component size, while simultaneously demanding these components to handle increasingly greater levels of power. As component size decreases and power levels increase, higher operating temperatures result. The presence of elevated temperatures of electric motors is attended by a variety of operational difficulties and malfunctions. For example, it is heat which does the most damage to permanent magnets contained within the electric motor. If the electric motor is severely overheated, diminished magnet strength, and hence degraded motor performance will take place.
There are several conventional methods for cooling electric motors. Natural convection cooling, for example, is a passive process involving the transfer of heat by the natural movement of air. Hot air tends to rise and is replaced by surrounding cooler, more dense air. Natural convection cooling includes several drawbacks, such as the small amount of dissipated heat that it is able to remove. Natural convection cooling does not allow for large enough amounts of heat to be removed in the time necessary to avoid operational difficulties. As stated above, electric motors carry large currents to produce high power, which results in high temperatures. As temperatures increase, operational difficulties and malfunctions may occur.
Lower motor operating temperatures result in an increase in motor efficiency. A lower motor temperature allows for more current to be carried by the motor windings, which in turn produces greater power output.
What is needed is an assembly and method that is able to remove large quantities of dissipated heat from electric motor end-windings. The larger the quantity of dissipated heat removed, the more efficient the motor will be, and consequently, the larger the amount of power that it will be able to handle.
To achieve the foregoing objectives, the present invention provides an assembly for cooling an electric motor; the assembly comprises a housing, a stator disposed within the housing operable for generating a magnetic field, a rotor disposed within the housing operable for receiving the magnetic field and generating a torque, a winding operatively connected to the stator, an end-winding integrally formed with the winding which hangs out of the stator stack, and a jet impingement device operable for exposing the end-winding to a temperature controlled stream of fluid.
The assembly further provides an inlet operable for introducing and exposing the temperature controlled stream of fluid to the end-winding, and an outlet operable for removing fluid from the housing. The inlet may comprise a nozzle which directs the temperature controlled stream of fluid to the end-windings.
The temperature controlled stream of fluid may comprise air or other fluid, and is generated in a temperature controlled fluid generating device, such as an air compressor. The air compressor may further include a pathway for the temperature controlled fluid from the temperature controlled fluid generating device to the inlet.
The present invention further provides a method for transferring heat between a stream of fluid impinging the surface of an electric motor end-winding, and the end-winding itself. The method comprises controlling the temperature of a volume of fluid, establishing a stream of fluid from the volume of fluid to an inlet, delivering the temperature controlled fluid from the inlet to the end-winding such that heat is transferred between the surface of the end-winding and the stream of fluid impinging the surface of the end-winding, and removing fluid from the electric motor via an outlet.
The present invention further provides an electric motor comprising a housing, a stator disposed within the housing operable for generating a magnetic field, a rotor disposed within the housing operable for receiving the magnetic field and generating a torque, a winding operatively connected to the stator, an end-winding integrally formed with the winding, and a jet impingement device operable for exposing the end-winding to a temperature controlled stream of fluid.